Get two bags of mesquite or pecan wood, they usually call them
"smokin' chunks" from HEB, Krogers, Randalls, any grocery store should have 'em.
Get a nice fire going in the firebox, let it burn down to coals, put your brisket on (fat side up) and then add a few chunks of wood to the fire. Let that go for about an hour, check it and just add more chunks as needed. It's pretty intuitive, you'll be able to judge how much to add and how often.
For a 12 lb. brisket you probably want to go about 9 - 10 hours.
Try to keep the temp. between 225 - 250.
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